Alan Turing was a mathematical genius whose work during World War II at Bletchley Park saved millions of lives. He led the team that cracked the German Enigma code, an encryption system thought to be unbreakable. Turing developed the 'Bombe,' an electro-mechanical device that could decipher Enigma-encrypted messages at high speed. Beyond his wartime heroics, he laid the theoretical foundations for the modern computer with his 'Universal Turing Machine' concept. He was also a pioneer in artificial intelligence, proposing the 'Turing Test' as a way to measure a machine's ability to exhibit intelligent behavior indistinguishable from a human.